1. Field of the Invention(s)
The present invention(s) generally relate to wireless transmitters. More particularly, the invention(s) relate to systems and methods for providing signals from multiple active wireless transmitters.
2. Description of Related Art
In microwave radio systems, transmitter backup systems are common. In a typical transmitter backup system, there is one main active transmitter and one or more other secondary “backup” transmitters. The secondary backup transmitters are muted and inactive while the main active transmitter transmits signals to a wireless receiver (e.g., a tower or other wireless signal receiving device). If the main active transmitter fails or is operating below an acceptable limit, the main active transmitter may be muted and one of the secondary backup transmitters becomes the main active transmitter. In the prior art, there is only one active transmitter at any one time.
FIG. 1 depicts a main active transmitting radio frequency unit (RFU) 102 and a secondary backup transmitting RFU 104 in the prior art. FIG. 1 implements a monitor hot standby (MHSB) approach. The MHSB configuration is often used when radio housing is designed to equip at least for two and more RFUs. In normal operation, both RFUs are in full power status and the two radios are connected to a high power switch 108 (e.g., an Antenna Coupling Unit (ACU)) or a Diplexer. One radio on the protected side (e.g., secondary backup transmitting RFU 104) is in the off position of the switch 108. The switch 108 may be either a reflective or an absorb switch. Power on both sides is monitored. When there is a failure, an alarm activates and the transmit path will switch from one side to the other. The failed RFU will then be replaced.
In one example, a main active transmitting RFU 102 in an environment 100 provides a wireless signal to a wireless communication tower 106 (e.g., cell tower or other microwave radio device) via an antenna 112. If the main active transmitting RFU 102 fails or falls below an acceptable level of performance, the switch 108 switches to the secondary backup transmitting RFU 102.
A failure detector device monitors one or both transmitting RFUs 102 and 104 for failure. When a failure is detected, a command may be sent to the switch 108 to switch to the other transmitting RFU. The signal is then provided to the antenna 112 via the diplexer 110. Unfortunately, switching from one transmitting RFU to the other causes a loss of performance and an interruption of service and, therefore, the system is not “hitless.”
FIGS. 2 and 3 depict a mute protected approach or cold standby (CSB). FIGS. 2 and 3 are often used when the RFU is optimized for a non-protected RFU. In one example, the protected radio (e.g., secondary inactive backup transmitting RFU 204) is muted. When there is a failure, the operator will first mute the problem transmitter, un-mute the protected RFU, then replace the failed RFU.
FIG. 2 depicts a main active transmitting RFU 202 and a secondary inactive backup transmitting RFU 204 with separate antennas 210 and 214 in the prior art. In an environment 200, a main active transmitting radio frequency unit 202 transmits data through the antenna 210 via the diplexer 208 to the wireless communication receiver 206. The secondary inactive backup transmitting RFU 204 may be muted or otherwise inactive. It is not uncommon that the secondary inactive backup transmitting RFU 204 is powered and ready to be made active thereby acting as a backup to the main active transmitting radio frequency unit 202.
If the main active transmitting RFU 202 fails or falls below an acceptable level of performance, the main active transmitting radio frequency unit 202 may be muted or become inactive and the secondary inactive backup transmitting RFU 204 may become active. As a result the formerly secondary inactive backup transmitting RFU 204 will become the primary transmitting unit and provide the signal to the antenna 214 via the diplexer 212 for transmission to the wireless communication receiver 206.
FIG. 3 depicts a main active transmitting RFU 302 and a secondary inactive backup transmitting RFU 304 with a single antenna in the prior art. Although an external coupler is depicted, the protected side is required to be muted because of potential interference and cancellation of two signals as a result of random phase characteristics.
In the environment 300, the main active transmitting RFU 302 and the secondary inactive backup transmitting RFU 304 are coupled via coupler 312 with the antenna 314. As similarly discussed with regard to FIG. 2, the main active transmitting RFU 302 transmits data through the antenna 314 via the diplexer 308 to the wireless communication receiver 306. The secondary inactive backup transmitting RFU 304 may be muted or otherwise inactive.
If the main active transmitting RFU 302 fails or falls below an acceptable level of performance, the main active transmitting RFU 302 may be muted or become inactive and the secondary inactive backup transmitting RFU 304 may become active. As a result, the formerly secondary inactive backup transmitting RFU 304 will become the primary transmitting unit and provide the signal to the antenna 314 via the diplexer 310 and the coupler 312 for transmission to the wireless communication receiver 306. The coupler 312 may provide faster communication over the antenna 314 than the switching element discussed with regard to FIG. 1. Unfortunately, activating one RFU and deactivating the other (e.g., based on unsatisfactory performance), causes a loss of performance and an interruption of service and, therefore, the system is not “hitless.”